Lilly markets Gemzar (gemcitabine)
for the treatment of
various forms of cancer. Both the '614 patent and the '826 patent cover gemcitabine
and are so listed in the U.S. Food and Drug Administration's (FDA) Approved
Drug Products with
Therapeutic Equivalence Evaluations (the Orange Book)
listing for Gemzar. The '614 patent claims gemcitabine, as well as a method of
using gemcitabine
for treating viral infections. The '826 patent, however,
claims a method of using gemcitabine for treating cancer.

Specifically, the specification of the '614 patent states:
"In addition to the antiviral utility of the present compounds,
certain of the
compounds of the present invention have also demonstrated excellent oncolytic
activity in standard cancer screens. A particularly
preferred compound with
this utility is [gemcitabine]."

On Dec. 4, 1984, the same day that Lilly
filed the
continuation-in-part that resulted in the '614 patent, Lilly filed another
patent application that ultimately issued as the '826 patent.
The '614 patent
does not claim a method of using any of the claimed nucleosides for treating
cancer. Each claim of the '826 patent is directed to a
method of treating
cancer with an effective amount of a class of nucleosides, which includes
gemcitabine.

Specifically, claim 1 of the '826
patent reads: "[a] method
of treating susceptible neoplasms [i.e.,
cancer] in mammals comprising administering to a mammal in need of such
treatment a therapeutically effective amount of the class of nucleosides."

Claim 2 of the '826 patent
is specifically directed to a
method of using gemcitabine.

After Sun Pharma filed an Abbreviated New Drug Application
(ANDA) with the FDA for
approval to market a generic version of Gemzar and
certified that both the '614 patent and the '826 patent were invalid or not
infringed, Sun filed
suit against Lilly to try to get a court judgment
affirming that the '826 patent is invalid and not infringed.

The district court sided with Sun that the claims of the
'826 patent are invalid for obviousness-type double patenting over
the earlier
'614 patent after it concluded—in light of the '614 patent's disclosure of
gemcitabine's anticancer use—that the claims are not
patentably distinct.

The doctrine of double patenting is intended to prevent a
patentee from obtaining
an extension of a patent for the same invention or an
obvious modification. The rule against double patenting takes two forms:
statutory double
patenting, which prohibits a later patent from covering the
same invention, i.e., identical subject
matter, as an earlier patent; and
obviousness-type double patenting, which is a
judicially created doctrine that prevents a later patent from covering a slight
variation of an earlier
patented invention.

Obviousness-type double patenting prohibits "claims in a
later patent that are not patentably distinct from claims in a
commonly owned
earlier patent. An obviousness-type double patenting analysis consists of two
steps. First, the court "construes the claim[s] in the
earlier patent and the
claim[s] in the later patent and determines the differences." Second, the court
"determines whether those differences render
the claims patentably distinct."

Lilly tried arguing that the double-patenting analysis did
not apply because
although the specification of the earlier '614 patent
disclosed gemcitabine's use in treating both viral infections and cancer, the
antiviral use
provided the essential utility necessary to the patentability of
the '614 patent's claim to gemcitabine. Lilly objected to what it said was the
district court's extension of the obviousness-type double patenting analysis to
any utility disclosed in the specification of an earlier patent.

The Federal Circuit summarily rejected Lilly's argument,
saying that the analysis in earlier
decisions show that obviousness-type double
patenting encompasses any use for a compound that is disclosed in the
specification of an earlier patent
claiming the compound and is later claimed
as a method of using that compound.

Thus, the rule
that a "claim to a method of using a
composition is not patentably distinct from an earlier claim to the identical
composition in a patent disclosing
the identical use," extends to any and all
such uses disclosed in the specification of the earlier patent. In affirming
the district court's decision
that the patent was invalid, the court wrote that
"[i]t would shock one's sense of justice if an inventor could receive a patent
upon a composition
of matter, setting out at length in the specification the
useful purposes of such composition … and then prevent the public from making
any beneficial
use of such product by securing patents upon each of the uses to
which it may be adapted."

The
take-home message is that if you have uses for a
compound that you intend to patent, you need to claim the uses on first
disclosure.